Automated contact alignment tool

ABSTRACT

A method for determining the alignment of a plurality of contacts in an electronic testing machine is disclosed. The contacts are swept over an electronic component taking a plurality of electrical readings. These electrical readings are charted against a desired orientation to determine alignment. Alignment can be corrected as necessary using an adjustment mechanism.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.11/838,706, filed Aug. 14, 2007.

FIELD OF THE INVENTION

The invention relates to the field of testing equipment for electroniccomponents and more particularly to the field of aligning test contacts.

BACKGROUND

Miniature electronic components are tested in a variety of ways. Onegroup of testing that relates to multiple layer capacitance chips (MLCC)involves electrical testing, including, but not limited to cap testing,cross checking, testing for leakage current, and testing for break downvoltage. In the example of U.S. Pat. No. 5,842,579 entitled ElectricalCircuit Component Handler, which is incorporated herein by reference,there is shown an example of a rotary style electronic testing machine10. With reference to FIG. 1 herein, which is a modification of FIG. 2from U.S. Pat. No. 5,842,579, an electronic component is captured in atest plate 12. A vacuum source passes a vacuum through a base plate todraw electronic components into component pockets on test plate 12.

As illustrated in FIG. 2 herein a stepper motor 16 is operativelyconnected to test plate 12 to index test plate 12 such that electroniccomponents are delivered to test heads 18 located on testing machine 10.Frequently the test heads are closely spaced. Each test head 18 mayinclude a plurality of test contacts, each test contact configured toconduct the same test. After the testing is complete, test plate 12continues to index to deliver tested components to blow off zone 22. Inblow off zone 22 the electronic components are blown out of thecomponent pocket that contains them and appropriately sorted as afunction of the test results. In the example of U.S. Pat. No. 5,842,579the blow off is accomplished by passing the component pockets over aplurality of blow off holes such that actuation of an air source througha specific blow off hole operates to sort the electronic componentsaccording to their individual test results.

Other configurations of test machines are also available. For example,the test plate, rather than being circular in shape may be rectangular.Also drums may be used for certain testing arrangements.

Electronic component testers may be adjusted and/or calibrated such thatthe individual test contacts properly align over component pockets suchthat when the test plate 12 is indexed the electronic components aredelivered to the contacts so that an acceptable electrical connection isachieved. One way to align the test contacts with the test componentpockets is the use of a fixture to assist the placement of test heads.Proper alignment can be more accurately realized by checking thealignment of the test heads with a borescope. In particular, theborescope would be used to visually inspect each contact and itsrelative positioning against the component pockets on the test plate.This evaluation would include inspection of theta and skew. If adetermination was made that the test contact or test head wasmisaligned, alignment could be achieved by known adjustments.

Because the test heads may be closely spaced, use of borescope may bedifficult and time consuming. A need has arisen to improve the processof determining the alignment of the contact heads.

SUMMARY

Other applications of the present invention will become apparent tothose skilled in the art when the following description of the best modecontemplated for practicing the invention is read in conjunction withthe accompanying drawings.

A method for determining a position of a plurality of test contacts onan electronic component testing machine is disclosed. The componenttesting machine includes a component test plate configured to retain aplurality of electronic components. The test plate is movable between aplurality of index positions such that electronic componentselectrically connect to the testing contacts at each index position. Theelectrical connectivity between an electronic component and a testingcontact is measured at a plurality of microsteps where each themicrostep is a fraction of an index. A plurality of electricalmeasurements is provided for an individual test contact. The pluralityof measurements is evaluated to determine the alignment of the testcontact.

A method for aligning at least one of a plurality of test contacts on anelectronic component testing machine is also provided. The componenttesting machine includes a test plate configured to retain a pluralityof electronic components and the test plate is movable between aplurality of index positions. Electronic components electrically connectto the plurality of testing contacts at each index. The method includesmeasuring the electrical connectivity between the electronic componentand a testing contact at a plurality of microsteps and a plurality ofelectrical measurements is provided for a single test contact. The testcontact is adjusted based on the plurality of electrical measurements.

An electronic component testing machine is also provided. The machineincludes a test plate configured to retain a plurality of electroniccomponents and includes a plurality of test heads. Each test head has aplurality of test contacts. The test plate is operatively connected to adrive mechanism such that the test plate is movable between a pluralityof index positions to deliver a plurality of electronic components toone of the test heads. A motion controller is configured to move thetest plate in microsteps where the microsteps are a distance less thanan index. A controller is configured to take multiple electricalmeasurements between an electronic component and an individual testcontact for each microstep resulting in a plurality of electricalmeasurements. Means are provided to adjusting the test contact to bringit into alignment based on the electrical measurements

BRIEF DESCRIPTION OF THE DRAWINGS

The description herein makes reference to the accompanying drawingswherein like reference numerals refer to like parts throughout theseveral views, and wherein:

FIG. 1 is a flow chart depicting the process of determining thealignment of test contacts and including an adjustment of the testcontacts;

FIG. 2 is a simplified perspective view of an electrical testing machinemodified according to one embodiment of the invention;

FIG. 2A is a simplified perspective view of a testing machine configuredto carry out the process of FIG. 1;

FIG. 3 is a close up plan view of a test pocket positioned over a pairof blow off holes;

FIG. 4 illustrates an optionally graphical output depicting the relativealignment of a plurality of test contacts on a plurality of test heads;

FIG. 5 is a representative example of an adjustment mechanism that willadjust positioning of a test head; and

FIG. 6 is a simplistic illustration of different pattern profiles ofmicrostep contact measurements for a test head.

DETAILED DESCRIPTION

In normal operation of an electronic test machine a test plate willindex from test head to test head. At each test head an electricalmeasurement will be made. It has been discovered that by dividing theindex into a plurality of microsteps an electronic component can beswept underneath a test contact to evaluate the location of a testcontact. In one example, the location of the electronic component may bemeasured relative to a fixed position on the test machine. This fixedposition may be at least one blow off hole positioned on a base plate ofthe test machine. Other fixed locations may be utilized as well. Thefixed position may be correlated against the position of a motor drivingthe test plate to provide a centerline. In the case of a test plate thatincludes electronic components drawn into component pockets by a vacuum,this fixed position on the machine could possibly become offset relativeto the test plate as the test plate becomes loaded with components. Insuch a case, both a loaded and an unloaded centerline may be provided.For each microstep a determination may be made whether an electricalconnection exists between the electronic component and the test contact.Based on the positioning of the plurality of electrical measurementsrelative to either centerline conclusions may be drawn with respect toalignment. The data derived from the measurements may be graphicallypresented to a user such that the user can draw conclusions with regardto alignment, or the system may evaluate the data and inform the userwhether adjustments are necessary and if so what those adjustments are.

With reference to FIG. 1 there is shown a flow chart illustrating theacts of the method of the present invention. With reference to act 31 atest mode is enabled. At act 31 sample components are loaded into testplate 12. At the test act 31 a motion controller 17 divides each indexinto a plurality of microsteps. These microsteps may be defined by motorsteps of a stepper motor and may be of an arbitrary distance. In oneexample where the test plate includes eight concentric rings of 200holes, an index may be approximately 1.8 degrees. In this example, theindex of 1.8 degrees may be divided into 200 microsteps, thus enablingthe test plate to advance 0.009 degrees for each microstep. As a rule ofthumb it has been discovered that dividing the microsteps into adistance approximating 1/20 of the width of the component being testedprovides useful results. However, the microstep may be a larger orsmaller fraction of the index size.

At act 33 the test plate is advanced by the above described microstepamounts. At act 34 the alignment system attempts to measure theelectronic connection between a test contact 20 and the electroniccomponent for each microstep. In one example the measurement is merelybinary, meaning the system determines, yes or no, whether a connectionhas been made. In act 36 the alignment of the test contact isdetermined. The alignment may be determined either automatically or withreference to a graphic representation of data.

With reference to FIG. 2A test machine 10 further includes controller 19configured to receive the data from act 34 and either graphicallypresents it, as in FIG. 4, or makes other calculations. Controller 19may be part of an overall controller for machine 10 or may be a separatecontroller.

With reference to FIG. 4 there is shown a graphical representation ofthe output of a microstep evaluation of the alignment of the pluralitytest contacts. In the illustrative example of FIG. 4 there is shown theevaluation of nine different contact heads, 40, 41, 42, 43, 44, 45, 46,47, and 48. Each contact head includes a plurality of contacts, e.g. 50,51, 52, 53, 54, 55, 56, and 57 which have each been individuallyevaluated. Another example of an evaluation an individual head is seenat 58. The vertical bar referenced as 58 represents a plurality ofsuccessful microstep connections between points A and B.

Individual contacts may be evaluated to determine whether the connectionbetween the test contact and the electronic component is consistent.With reference to head 59 there is shown a collection of microstepconnections where for a portion of the microsteps e.g. 60 where noelectrical connection could be made between the test contacts and theelectronic component. This illustration would inform the operator thatthere was intermittent contact between the test contact at 59 and itsassociated component. An operator may remedy this in a variety of waysincluding replacement of the test contact at 59.

FIG. 4 further illustrates an unloaded nominal center indicator line 70.Unloaded nominal center indicator line 70 references the positionalcenterline of the component pocket when the test plate is moving andunloaded. The measurement is made from a fixed position on the machinewhen the test plate is unloaded and moving.

One example of determining a centerline is shown in FIG. 3. Inparticular when the test plate is moving a pair of blow off holes 23 maybe observed and positionally correlated against a motor count location.In the example of FIG. 4 the number of motor counts per angle ofrotation of the test plate may be determined. The component pockets 21center themselves over the blow off holes 23 at a repeatable motorcount. In the example of FIG. 4 this repeatable motor count isarbitrarily set at a zero motor count when the test plate is rotatingand empty, as noted by reference numeral 70. It has been observed thatin operation of certain electronic component testing machines, such asthe model 3430 as sold by Electro Scientific Industries, Inc., theassignee of the instant application, a dynamic shift offset from thecenterline occurs as the test plate is loaded with electroniccomponents. That is, the rows of component pockets center themselvesover the blow off holes 23 at a slightly different motor count whenloaded. One cause of this dynamic shift is the vacuum utilized to retainthe electronic component pockets. In the example of FIG. 4 the dynamicshift was measured as approximately 15 positive motor counts. Thus, insome examples a dynamic centerline 71 may be provided. An upper connectlimit 72 and a lower contact limit line 73 may also be provided. In theexample of FIG. 4 the upper contact and lower contact limit linesprovide suggestive limits where the test components within whichcomponent pockets 21 should be found. In the example of FIG. 4 aconnection between the electronic component and the test contacts isexpected to occur between a positive 30 motor counts to a minus 15 motorcounts.

With reference again to FIG. 1, act 37 queries as to whether the testheads are aligned. If the test heads are not aligned, the test heads maybe aligned at act 38. Act 38 involves adjusting the test contacts and/ortest head such that they would be properly aligned with the testcomponent received in the component pocket 21 in the test plate 12. Withreference to the example of FIG. 4 one way to make this adjustment wouldbe as follows. Looking to the microstep measurements taken at 48 it canbe seen that the measurements are biased in a leading direction. Atleast some of the microstep measurements in the example did not achievea connection at the dynamic centerline 71. Thus an adjustment may bemade to shift the test head in the direction of arrow “C”.

With reference to FIG. 5 there is shown a simplified test head 18including a plurality of test contacts 20. Test head 18 is illustratedwith reference to a test plate 12 and component pockets 21. As isillustrated in FIG. 5 test head 18 may include adjustments for y skew75, a y adjustment 77 and a theta adjustment 79. Movement of theaforementioned adjustments in the example of FIG. 5 will move test head18 in the y skew direction 76, the y direction 78 and the thetadirection 80.

In the context of measuring connections at act 34 of FIG. 1, theresulting data may inform a user of adjustments to a test head 18 toimprove the alignment of the test head relative to the connect pockets.In the example of FIG. 4 alignment information is graphically displayedto a user who may then interpret the data and adjust the test head. Inan alternate example the measurement data may be mathematicallyinterpreted and a user may be specifically informed of the adjustment tobring the test head into alignment. For example, this adjustment mayinform the user to turn the theta adjustment one turn clockwise.

As shown with respect to head 48 in FIG. 4 the measurement results arepreferably in a tapered pattern. This tapered pattern is a function oftest plate 12 being circular. It is understood that a non-circular testplate may not yield a tapered pattern of measurement results. The y skewadjustment 75 affects the taper of the measurements.

With reference to FIG. 6 there are shown example profile patterns wherethe taper is skewed and y skew adjustment may be advisable. In theexample 82 the y skew is correct for a circular test plate. In theexample of 84 y skew is clockwise oriented and needs to be adjustedcounter clockwise. In the example of 86 y skew is counter clockwiseoriented and needs to be adjusted clockwise.

With reference again to the example of FIG. 1, after an adjustment hasbeen made, act 32 may be reinitiated to confirm alignment. Reinitiatingact 32 may not be necessary and may depend on customer preferences. Ifthe query at act 37 indicates alignment, either determined automaticallyor by reference to a graphic illustration, the process is complete atact 39.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiments but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims, which scope is to be accorded the broadestinterpretation so as to encompass all such modifications and equivalentstructures as is permitted under the law.

1.-17. (canceled)
 18. An electronic component testing machine, themachine including a test plate configured to retain a plurality ofelectronic components; the machine further including a plurality of testcontacts and the test plate operatively connected to a motor such thatthe test plate is movable between a plurality of index positions suchthat each test contact comes into contact with a distinct electroniccomponent to perform a discrete electrical test, the improvementcomprising: a motor controller configured to move the test plate inmicrosteps, the microsteps being a distance less than an index; acontroller configured to take multiple electrical measurements betweenan electronic component and a test contact for each microstep such thata plurality of electrical measurements is made between the test contactand at least one electronic component; and means for adjusting the testcontact to bring it into alignment based on the plurality of electricalmeasurements.
 19. The electronic component testing machine as in claim18 wherein the adjusting means comprises an adjustment screw configuredto adjust a test head associated with the test contact.
 20. Theelectronic component testing machine as in claim 18 wherein theadjusting means comprises an adjustment screw configured to adjust thetest contact.
 21. The electronic component testing machine as in claim19 wherein the adjustment screw is configured to adjust the test contactin a theta orientation.
 22. The electronic component testing machine asin claim 18 wherein the motor is a stepper motor.
 23. The electroniccomponent testing machine as in claim 18 wherein the controller isfurther configured to evaluate the plurality of electrical measurementsto determine the alignment of the test contact.
 24. The electroniccomponent testing machine as in claim 18 wherein the adjusting meansadjusts the test contact relative to a centerline, the centerline beinga function of a fixed position on the test machine.
 25. An electroniccomponent testing machine, the machine including a test plate configuredto retain a plurality of electronic components; the machine furtherincluding a plurality of test contacts and the test plate operativelyconnected to a motor such that the test plate is movable between aplurality of index positions such that each test contact comes intocontact with a distinct electronic component to perform a discreteelectrical test, the improvement comprising: a motor controllerconfigured to move the test plate in microsteps, the microsteps being adistance less than an index; and a controller configured to takemultiple electrical measurements between an electronic component and atest contact for each microstep such that a plurality of electricalmeasurements is made between the test contact and at least oneelectronic component and the controller configured to evaluate theplurality of electrical measurements to determine an alignment of thetest contact.
 26. The electronic component testing machine as in claim25, further comprising: an adjustable connection supporting the testcontact for adjustably bringing a misaligned test contact into alignmentbased on an evaluation of the plurality of electrical measurements. 27.The electronic component testing machine as in claim 25 wherein thealignment of the test contact is whether an intermittent contactcondition exists.
 28. The electronic component testing machine as inclaim 25 wherein the controller is configured to evaluate the pluralityof electrical measurements by comparing measurements for a singlecontact against a centerline to determine whether the alignment isleading or lagging.
 29. The electronic component testing machine as inclaim 28 wherein the centerline is between a pair of blow off holeslocated on the electronic testing machine.
 30. The electronic componenttesting machine as in claim 28 wherein the centerline is a dynamiccenterline.
 31. The electronic component testing machine as in claim 25wherein each index comprises about 200 microsteps.
 32. The electroniccomponent testing machine as in claim 25 wherein each test contact ispart of a test head, the test head including a plurality of testcontacts.
 33. The electronic component testing machine as in claim 25wherein the test head includes a theta adjustment and a y skewadjustment.